New data on early-stage trials of Johnson & Johnson’s Covid-19 vaccine are giving experts increased confidence that the vaccine will work as they await results of a large Phase 3 trial expected in the coming weeks. The trial data, published Wednesday by the New England Journal of Medicine, offered an expanded and updated account of a paper posted weeks ago on a so-called preprint server. The paper showed that 90% or more of participants developed neutralizing antibodies against the virus that causes Covid-19 within 29 days after injection with the Johnson & Johnson vaccine, and that the neutralizing antibodies remained 71 days after injection. Shares of Johnson & Johnson were up 1.8% in premarket trading on Thursday.